tests: Always cleanup gpg-agent when exiting

Add `libtest_cleanup_gpg()` to the array of commands to run when
exiting. This provides 2 improvements:

1. You don't need to worry about whether the test will spawn a gpg-agent
   and therefore require adding a call to `libtest_cleanup_gpg()`.

2. All the existing users were calling `libtest_cleanup_gpg()` at the
   end of the script. If there was a failure and the script exited
   early, then it wouldn't cleanup and there may be a stray gpg-agent
   hanging around.

Closes: ostreedev#1799
Approved by: cgwalters

tests/libtest.sh

@@ -648,6 +648,7 @@ libtest_cleanup_gpg () {
     local gpg_homedir=${1:-${test_tmpdir}/gpghome}
     gpg-connect-agent --homedir "${gpg_homedir}" killagent /bye || true
 }
+libtest_exit_cmds+=(libtest_cleanup_gpg)
 
 is_bare_user_only_repo () {
   grep -q 'mode=bare-user-only' $1/config

tests/test-commit-sign.sh

@@ -140,4 +140,3 @@ assert_not_file_has_content show.txt 'Found.*signature'
 echo "ok pull sig deleted"
 
 rm -rf repo gnomerepo-files
-libtest_cleanup_gpg

tests/test-gpg-signed-commit.sh

@@ -89,8 +89,6 @@ if ${OSTREE} show test2 | grep -o 'Found [[:digit:]] signature'; then
   assert_not_reached
 fi
 
-libtest_cleanup_gpg
-
 echo "ok"
 
 # Remaining tests require gpg

tests/test-pull-mirror-summary.sh

@@ -120,5 +120,3 @@ echo "ok pull mirror with invalid summary sig and no verification"
 # assert_file_has_content deltas.txt "${origmain}-${newmain}"
 
 # echo "ok pull mirror with signed summary covering static deltas"
-
-libtest_cleanup_gpg

tests/test-pull-summary-sigs.sh

@@ -274,5 +274,3 @@ cmp repo/tmp/cache/summaries/origin ${test_tmpdir}/ostree-srv/gnomerepo/summary.
 cmp repo/tmp/cache/summaries/origin.sig ${test_tmpdir}/ostree-srv/gnomerepo/summary.sig.2 >&2
 
 echo "ok pull with signed summary broken cache"
-
-libtest_cleanup_gpg

tests/test-remote-gpg-import.sh

@@ -280,5 +280,3 @@ ${CMD_PREFIX} ostree --repo=${test_tmpdir}/ostree-srv/gnomerepo summary -u --gpg
 ${OSTREE} pull --require-static-deltas R1:main
 
 echo "ok gpg trusted signed commit for delta upgrades"
-
-libtest_cleanup_gpg

tests/test-summary-view.sh

@@ -62,5 +62,3 @@ assert_file_has_content_literal raw-summary.txt "('main', ("
 assert_file_has_content_literal raw-summary.txt "('other', ("
 assert_file_has_content_literal raw-summary.txt "{'ostree.summary.last-modified': <uint64"
 echo "ok view summary raw"
-
-libtest_cleanup_gpg